U.S. patent application number 11/739213 was filed with the patent office on 2007-11-01 for system and method to measure parameters distribution in sheet-like objects.
Invention is credited to Sergey Kholchanskiy, Victor Milovidov, Victor Preobrazhenskiy, Nadejda Reingand, Igor Zelenyak.
Application Number | 20070252592 11/739213 |
Document ID | / |
Family ID | 38647729 |
Filed Date | 2007-11-01 |
United States Patent
Application |
20070252592 |
Kind Code |
A1 |
Kholchanskiy; Sergey ; et
al. |
November 1, 2007 |
SYSTEM AND METHOD TO MEASURE PARAMETERS DISTRIBUTION IN SHEET-LIKE
OBJECTS
Abstract
A measuring device and method are disclosed for parameter
distribution measurement over the entire surface of sheet-like
objects. The parameters of primary interest are thickness and
permeability profiles. The device includes a parameter measuring
unit a coordinate measuring unit and a synchronization unit to
control operation of the parameter measuring unit and the
coordinate measuring unit. The coordinate measuring unit determines
the measuring device position on two-dimensional surface using
image correlation analysis. The measuring device further comprises
a platform for its movement in the plane of the sheet-like
object.
Inventors: |
Kholchanskiy; Sergey;
(St.Petersburg, RU) ; Preobrazhenskiy; Victor;
(St. Petersburg, RU) ; Zelenyak; Igor;
(St.Petersburg, RU) ; Milovidov; Victor;
(St.Petersburg, RU) ; Reingand; Nadejda;
(Baltimore, MD) |
Correspondence
Address: |
Nadejda Reingand
7 Clifton Ct.
Baltimore
MD
21208
US
|
Family ID: |
38647729 |
Appl. No.: |
11/739213 |
Filed: |
April 24, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60795751 |
Apr 29, 2006 |
|
|
|
Current U.S.
Class: |
324/229 |
Current CPC
Class: |
G01B 7/06 20130101 |
Class at
Publication: |
324/229 |
International
Class: |
G01B 7/06 20060101
G01B007/06 |
Claims
1. A measuring device for measuring a spatial distribution of at
least one parameter of a sheet-like object, comprising: a parameter
measuring unit for measuring a parameter at least at a point A and
a point B on an object surface, a coordinate measuring unit for
measuring a coordinate at least at the point B relative to the
point A on the object surface, the coordinate measuring unit being
connected to a digital signal processing unit, the coordinate
measuring, unit performing the coordinate measuring by determining
a correlation between a first image of a spot around the point A at
a time T.sub.1 and a second image of a spot around the point B at a
time T.sub.2, the first and the second images being taken by a
digital camera, a synchronization unit connected to the parameter
measurement unit and to the coordinate measuring unit, the
synchronization unit adapted to turn on the coordinate measuring
unit simultaneously with the parameter measuring unit; moving
platform to perform a displacement of at least the parameter
measuring unit and the coordinate measuring unit together in any
direction within the object surface, wherein the displacement
consists of steps, a length of each step being smaller than a
length of the spot around the point. A in a direction of the
displacement.
2. The measuring device according to claim 1, further comprising
magnetic holders to attach the sheet-like object to the parameter
measuring unit and the coordinate measuring unit.
3. The measuring device according to claim 1, wherein the parameter
is a thickness of the sheet-like object.
4. The measuring device according to claim 3, wherein the parameter
measuring unit is an inductive transducer for measuring the
thickness of the sheet-like object.
5. The measuring device according to claim 3, wherein the thickness
of the object is from 0.1 mm to 10 mm.
6. The measuring device according to claim 1, wherein the parameter
measuring unit is a permeability transducer for measuring a
permeability of the sheet-like object.
7. The measuring device according to claim 1, wherein the moving
platform comprises at least one spherical rotating element.
8. The measuring device according to claim 1, wherein the moving
platform further comprises a motor adapted for driving at least the
parameter measuring unit and the coordinate measuring unit together
along a preprogrammed trajectory in any direction within the object
surface.
9. The measuring device according to claim 8, wherein the
programmed trajectory is chosen to provide complete information
bout the object parameter distribution cover the object surface in
a shortest time.
10. The measuring device according to claim 1, wherein the object
is a fabric, a paper, a plastic sheet, a foil, a metal sheet or a
felt.
11. The measuring device according to claim 1, wherein the object
surface is at least 10 meters long in the direction of the
measuring.
12. The measuring device according to claim 1, wherein the
coordinate measuring unit further comprises a light source for
illuminating the spot around the measuring point A and the spot
around the measuring point B, a storage buffer to store at least
the first image of the spot around the point A taken at the time
T.sub.1 and the second image of the spot around the point B taken
at the time T.sub.2.
13. The measuring device according to claim 1, wherein the
parameter measuring unit the coordinate measuring unit, the
synchronization unit and the moving platform form a first and a
second block, the first block being positioned on a first side of
the sheet-like object surface and the second block positioned on a
second side of the sheet-like object surface the second block being
positioned symmetrical to the first block relative to the
sheet-like object.
14. The measuring device according to claim 1, wherein the digital
signal processing unit is located on distance R from the sheet-like
object, where R is from 10 cm to 100 meters.
15. A method of measuring a distribution of at least one parameter
of a sheet-like object, comprising: positioning at least a
parameter measuring unit and a coordinate measuring unit on a
sheet-like object surface at a point A, sending a first signal from
a synchronization unit to initiate simultaneous operation of the
parameter measuring unit and the coordinate measuring unit,
recording a first measured parameter in a digital signal processing
unit and a first image of a spot around the point A taken by a
digital camera in a buffer of the coordinate measuring unit, moving
at least the parameter measuring, unit and the coordinate measuring
unit in any direction within the object surface on a step distance
being less than a size of the spot in a direction of a
displacement, sending a second signal from a synchronization unit
to initiate simultaneous operation of the parameter measuring unit
and the coordinate measuring unit, recording a second measured
parameter in the digital signal processing unit and a second image
of a spot around the point B in the buffer, sending the first and
the second images from the buffer to a digital signal processing
unit, determining a first coordinate, a second coordinates and a
magnitude of the displacement and the direction of the displacement
by comparing a microstructure in the first and the second images,
displaying in graphics at least the first and the second parameters
in association with the first and the second coordinates.
16. The method of claim 15, wherein the microstructure comparing
includes correlation analysis.
17. The method of claim 15, wherein the first and the second
parameter are the sheet-like object thickness in the points A and B
respectively.
18. The method of claim 15, wherein the first and the second
parameters are the sheet-like object permeability, in the points A
and B respectively.
19. The method of claim 15, wherein the coordinate measuring unit
further comprises a light source for illuminating at least the spot
around a point A at a time T.sub.1, and the spot around a point B
at a time T.sub.2, a digital camera for capturing the images of the
spot around the point A and around the point B, a buffer to store
at least the first image of the spot around the point A taken at
the time T.sub.1 and the second image of the spot around the point
B taken at the time T.sub.2.
20. The method of claim 15, further comprising moving at least the
parameter measuring unit and the coordinate measuring unit in any
direction within the object surface on an entire measurement
distance, wherein the entire measurement distance is divided into a
number of the step distances, measuring a parameter and a
coordinate at each point at the step distances along the moving
trajectory, displaying the spatial distribution of the parameter in
graphics.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Ser. No. 60/795,751
filed Apr. 29, 2006, which is fully incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a measuring system and
method to determine parameters of a sheet-like object, especially a
fabric (including forming fabric), press felt, cloth and paper.
Said parameters include thickness and permeability profiles over
the entire surface of the object.
BACKGROUND OF THE INVENTION
[0003] It is known that the quality of the finished paper product
in paper manufacturing process depends to a large extent upon the
press felt. Therefore it is very important for paper manufacturer
to get knowledge about the press felt prevailing condition and
properties, such as thickness, tension profile, permeability, etc.
There is a need to provide reliable measuring devices and methods,
which are capable of mapping those properties over the entire
surface of the fabric. The width of the fabric, up to 10 meters and
sometimes greater, makes it difficult to carry out these
measurements.
[0004] Typically the thickness of the fabric is measured by a dial
indicator; which allows measuring only a few points across the
fabric. There are two main disadvantages of this method. Firstly,
it is impossible to get an entire thickness profile of the fabric.
And secondly, since the measurement is manual, it is difficult to
obtain an exact coordinate across the width of the fabric for the
point being measured. Due to these uncertainties, it is difficult
to compare thickness results measurements performed at different
time.
[0005] Current devices for thickness measurement to do not allow
changing measurement trajectory, repeating measurements in some
critical areas of an object, moving backwards, and in general
choose a two-dimensional trajectory being optimal for a particular
object under study. There is a need for a measurement device being
able to move in any direction within the plane of the object.
[0006] The problems described above in conjunction with the
measurement of the thickness profile also apply to the measurement
of the tension profile, permeability and other parameters of the
sheet-like objects. There is a need to repeatedly carry out
measurements of these parameters over the entire surface of the
fabric in a simple and reliable way.
SUMMARY OF THE INVENTION
[0007] The object of the present invention is to provide a
measuring device, which is capable of measuring the parameters of a
thin sheet object. The objects include fabric, cardboard, paper,
press felt, cloth and plastic materials. The parameters of primary
interest are the sheet-like object thickness profile and
permeability over the entire surface of the object. The object may
be up to 100 meter wide and up to 10 km long. In the preferred
embodiment the object is 10 meter wide and 300 m long.
[0008] The measurement device of the present invention has a
parameter measuring unit combined with a coordinate measuring unit.
The units simultaneously measure the parameter and coordinate,
respectively, at the particular point on the object surface being
synchronized by a synchronization unit. The parameter measuring
unit and the coordinate measuring unit move in the object surface
plane in any direction periodically recording data for further
digital signal processing. The coordinate measuring unit records
images of a light spot around a point of measurement on the surface
and store the images in a buffer. The light spot is created by
illumination of the surface by a light source. A digital signal
processing (DSP) unit is adapted to compare the images recorded
sequentially when the coordinate measuring unit moves over the
object surface. The images taken at sequential time moments are not
the same, but they have at least 10% of image being taken from the
same area of the surface. In other words, some parts of the
sequential images are overlapping. The coordinate measurement is
performed by correlation analysis of the sequential images.
[0009] In the preferred embodiment the parameter measuring unit
performs the object thickness measuring using an inductive
transducer. The thickness of the object is from 0.1 to 10 mm.
[0010] In another embodiment the parameter measuring unit performs
the object permeability measurement.
[0011] In yet another embodiment the measuring device includes
magnetic holders to attach the sheet-like object to the parameter
measuring unit and the coordinate measuring unit.
[0012] In yet another embodiment the measuring device includes a
moving platform for the parameter and coordinate measuring units
motion over the object surface, which optionally may include a
motor adapted for driving the units together along a preprogrammed
trajectory in any direction within the object surface. The moving
platform may have spherical elements as wheels.
[0013] In the preferred embodiment the parameter measuring unit,
the coordinate measuring unit, the synchronization unit, and the
moving platform form a first and a second block, the first block
being positioned on a first side of the sheet-like object surface
and the second block positioned on the second side of the
sheet-like object surface, the second block being symmetrical to
the first block relative to the sheet-like object.
[0014] A method to perform parameter distribution measurement for
sheet-like materials is another object of the present invention.
The method includes positioning at least a parameter measuring unit
and a coordinate measuring unit on a sheet-like object surface at a
point A, sending a first signal from a synchronization unit to
initiate simultaneous operation of the parameter measuring unit and
the coordinate measuring unit, recording a first measured parameter
in a digital signal processing unit and a first image of a spot
around a point A taken by a digital camera in a buffer, moving at
least the parameter measuring unit and the coordinate measuring
unit in any direction within the object surface on a step distance
being less than a size of the spot in a direction of a
displacement, sending a second signal from a synchronization unit
to initiate simultaneous operation of the parameter measuring unit
and the coordinate measuring unit, recording a second measured
parameter in the digital signal processing unit and a second image
of a spot around the point B in the buffer, sending the first and
the second image from the buffer to the digital signal processing
unit, determining a first coordinate, a second coordinates and a
magnitude of the displacement and the direction of the displacement
by comparing a microstructure in the first and the second images,
displaying in graphics at least the first and the second parameters
in association with the first and second coordinates.
[0015] The direction of the measuring device movement is not
limited to the direction perpendicular to the edge of the measured
surface, but it is chosen to optimize the measurement time and
quality.
[0016] It is another object of the present invention to perform
multiple measurements along two-dimensional trajectory over the
object surface and to obtain the parameter distribution over entire
surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1. A block diagram of the device to be used for
measuring the parameters distribution in sheet-like objects.
[0018] FIG. 2. A block diagram of the coordinate measuring
unit.
[0019] FIG. 3. A fabric with microstructure as an example of the
object under study.
[0020] FIG. 4. An illustration of the coordinate measuring unit
operation.
[0021] FIG. 5. Images of the object under study before and after
the object displacement.
[0022] FIG. 6. A block diagram of the thickness measuring unit.
[0023] FIG. 7. An illustration of the measuring device movement
over the object surface.
[0024] FIG. 8. An example of the measuring device consisted of two
blocks.
[0025] FIG. 9. Examples of programmed moving trajectories for the
measuring device: (a) a zig-zag, (b) a grid, (c) a repetitive
scanning of the critical area.
[0026] FIG. 10. Top (a) and side (b) views of one embodiment of the
measuring device of the present invention.
[0027] FIG. 11. Experimental results: (a) a spatial distribution of
the press felt thickness, (b) temporal change of the press felt
thickness.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0028] A measuring device according to the present invention
consists of following units with a connection between them as shown
in FIG. 1. Unit 1 is a coordinate measuring unit based on
correlation method. Unit 2 is a measuring device to determine
particular parameter of the thin sheet object under study. In the
preferred embodiment the parameter is the object's thickness. Unit
3 is a synchronization unit that ensures turning on Units 1 and 2
simultaneously by sending signals 4 and 5 to start measurement of
coordinate (Unit 1) and object parameter (Unit 2) at the same
moment. Data from Unit 1 and Unit 2 enters digital signal
processing (DSP) Unit 6 through channels 7 and 8. Unit 6 is adapted
to store and process the data from Units 1 and 2, recover
displacement magnitude and parameter value, and then to display the
data on a screen 9. At least Units 1 and 2 are positioned on a
moving platform 10, which optionally has holder 11 to attach the
device to the surface of the object 12. The platform 10 may
optionally be controlled by the DSP Unit 6 via link 13 to control
platform moving along predetermined trajectory.
[0029] Block diagram of Unit 1 for coordinate measurement is shown
in FIG. 2. Light source 20 irradiates light beam 21 and illuminates
a spot 22 on an object under study 12. Reflected light beam 24, is
collected by optoelectronics imaging device 25. Imaging device 25
outputs electrical signal 26. Gate 27 lets the signal 26 through
when the control signal 4 triggers it. Output signal 28 is stored
in a buffer 29. The signal 7 outputs Unit 1 for further processing
in the DSP Unit 6 as shown in FIG. 1.
[0030] Light emitting diodes are good candidates for light source
20. For example, RL5-W8045 White LED from Super Bright LEDs, Inc
(St. Louis, Mo.) with 2500 mcd output luminous intensity and 45
Degree viewing angle can be used.
[0031] CCD camera such as MC-F433 Color 30 fps Firewire Camera from
1 st Vision, Inc. (Andover, Mass.) can be used as an imaging device
25. The imaging device may optionally include additional optical
elements such as lenses, filters, pinholes or other element to
improve the quality of image captured by CCD matrix. Camera
parameter must allow resolving micro features of image of about 0.1
to 1 mm as shown in FIG. 3. A fabric is used as an example of the
object in FIG. 3.
[0032] Unit 1 measures coordinate in the manner similar to known
displacement measurement using correlation method, see, for
example, Feiel et al. "High resolution laser speckle correlation
for displacement and strain measurement", incorporated herein by
reference. Speckle structure serves as micro features in the system
disclosed in the above-mentioned article. Any other types of micro
features as long as they have irregular structure can be used for
image processing in correlation method.
[0033] FIG. 4 helps to explain how Unit 1 operates. An image of the
particular spot 22 is captured by the imaging device 25 and outputs
through gate 27 to be stored in the buffer 29. It serves as an
initial point of measurement, a zero-coordinate. Further measured
coordinates are related to this initial position of the coordinate
measuring Unit 1. Then the object displacement takes place, which
may happen in arbitrary direction in the plane of the object. It is
indicated by a vector 28 in FIG. 4. A new image of a new spot 22'
is captured that includes a part of image 22. In other words images
22 and 22' correspond to the parts of the surface under study that
are partially overlap. The new image 22' outputs through gate 27 to
be stored in the buffer 29 and further processed in the DSP Unit 6
(not shown in FIG. 4). The magnitude of the displacement 28 is
always smaller that the size of the image 22 in the direction of
the displacement. This ensures images overlapping. Images 22 and
22' are shown in FIG. 5 where the vector 28 indicates the direction
and a magnitude of the displacement. Framed areas 22 and 22' in
FIGS. 5 (a) and 5 (b) have the same microstructure. The processing
Unit 6 performs coordinate calculation based on image correlation
analysis.
[0034] Alternatively the whole system for thin sheet object
parameters measurement, which includes Unit 1 can be displaced
relative to an unmoving object.
[0035] Unit 2 is an object parameter measuring unit. It can be a
device for measuring sheet-like material thickness as shown in FIG.
6, but not limited to this example. The examples of thin object
measurement device may include ones based on local resistance
measurement, contact profilometers, non-contact optical devices and
others.
[0036] Thickness measuring unit shown in FIG. 6 comprises
essentially of a gauge 30 and a gate 32. The gauge 30 performs the
thickness measurement of the object 12 by known inductive method,
see for example U.S. Pat. No. 4,695,797 by Deutsch et al.,
incorporated herein by reference. In the preferred embodiment the
range of the object thickness is from 0.1 mm to 10 mm. The gauge 30
outputs signal 31. Gate 32 lets the signal 31 through when the
control signal 5 triggers it. Thus the signal 8 outputs Unit 2 at
the particular moment determined by the signal 5 coming from
synchronization Unit 3 as shown in FIG. 1. The moment of the
parameter measurement coincides with the moment of coordinate
measurement by Unit 1.
[0037] The holder 11 in FIG. 1 serves to ensure contact of the
object under study 12 and the gauge 30, being a part of Unit 1. The
holder 11 can be a known magnetic holder. Alternatively the holder
11 can be a known low-pressure holder that attaches sheet material
to the measuring device by creating a pressure below atmospheric
pressure.
[0038] The disclosed measuring device includes Units 1, 2, 3, and 6
as mentioned in the description above. Either the object under
study or the measuring device moves relatively each other during
the measurement procedure. It should be pointed out that the
measuring device can be split into two parts, one of which is a
moving part and another is a stationary one. Units 1 and 2 must be
in the moving part, however Units 3 and 6 may be included both or
separately in the moving part or may be stationary part connected
to the moving part by flexible links. Alternatively,
synchronization Unit 3 and DSP Unit 6 may be connected with Units 1
and 2 by means of wireless connection.
[0039] FIG. 7 illustrates the movement of measuring device 40
relatively the object under study on the moving platform 10. The
movement of the measuring device that includes at least Units 1 and
2 (and optionally Units 3 and 6) relative to the sheet-like object
12 is a two-dimensional movement in the plane of the object 12. The
present invention proposes application of spheres 41, 42, 43 to
perform this type of movement as shown in FIG. 7. Similar moving
platform is disclosed in U.S. Pat. No. 6,128,853 by Klonel et al.,
incorporated herein by reference. The number of spheres can be
larger or less than three shown in FIG. 7. Application of spheres
provides an example of two-dimensional movement platform in the
plane of the object under study; however the invention is not
limited to this example.
[0040] The measuring device of the present invention may consist of
two blocks, one of which (40a) is located to the top of the sheet
object 12 and the second block (40b) is attached to the bottom of
the object 12 as shown in FIG. 8. This configuration is typical,
for example, for inductive transducers for thickness measurement
devices. If the object is vertical, then the blocks 40a and 40b
will be on the right and on the left side of the object
respectively.
[0041] Both blocks 40a and 40b are moving relative to the object 13
using, for example, sets of spheres 41a, 42a, 43a and 41b, 42b,
43b. The amount of spheres can be larger or less than six shown in
FIG. 8, they maybe positioned on both upper and lower blocks or
simply on one of the blocks. In the preferred embodiment the Parts
40a and 40b are coupled by magnetic holders.
[0042] In one embodiment of the present invention the moving
platform can be preprogrammed for autonomic omni-directional
movement in the plane of the object. An example of such robotic
platform is disclosed in U.S. Pat. No. 5,374,879 by Pin et al.,
incorporated herein by reference.
[0043] Two-dimensional moving platform can be pre-programmed by the
DSP Unit 6 to perform the movement along trajectory, which is
optimal for performing measurements for a particular type of object
under study. Signal 13 from the DSP Unit 6 that controls motion of
the platform 10 is shown in FIG. 1. As an example, the moving
platform can be programmed to move forming a diagonal path 50 on
the surface of the object 12 as shown in FIG. 9(a). The
optimization of the measurement time can be achieved for example by
such diagonal movement of the measuring device on the measured
surface. Another example is associated with moving objects such as
a fabric or paper sheet moving on a production conveyor. The speed
of the conveyor movement and an angle of the measuring device
movement can be synchronized in the manner providing the optimal
performance of the object measurement, such as a thickness of the
fabric.
[0044] Another example is shown in FIG. 9 (b). The measurement is
performed in along X and Y directions with a distance between
consecutive parallel paths according to required measurement
resolution. Another example shown in FIG. 9 (c) demonstrates
multiple paths of the measuring unit in some critical area C of the
object surface. The system allows repeated measurement of the
critical spots on the measured surface to ensure the best accuracy.
These repeated measuring of particular spot parameters does not
require return of the measuring device to the initial position near
the edge of the measured surface.
[0045] Possible trajectories are not limited to above mentioned
examples. These examples illustrate advantages of omni-directional
moving platform compared to one-dimensional moving disclosed in
prior art.
[0046] The disclosed device and method is not limited to objects
having straight edges, but can be implemented to any kind of thin
sheet objects.
[0047] The measuring unit is not limited to the thickness measuring
device. It may be, for example, a permeability measuring unit for a
sheet-like material. U.S. Pat. No. 6,971,261 by Ischdonat et al.
discloses a fabric permeability device for paper production line.
The device comprises a nozzle aimed at a surface of the moving
clothing, the nozzle producing a water flow, which is measured at
the opposite side of the clothing. The clothing permeability is
determined on the basis of the measured flow.
[0048] Another example of measuring unit is an apparatus for
detection of holes and plugged spots on a fast running fabric such
as described in U.S. Pat. No. 5,725,737 by Pikulik et al.
Experimental Results
[0049] FIGS. 10 (a) and (b) show top and side view of one
embodiment of the device of the present invention. It consists of
two blocks 40a and 40b attached to the opposite sides of the object
12. The device performs thickness measurement using inductive
method. The parameter measuring Unit 2, the coordinate Unit 1 and
synchronization Unit 3 are located in the center of the device.
Both blocks 40a and 40b have magnetic holders 6c and manually moved
along the selected trajectory using the wheel 41. Two handles 51
and 52 are attached on both sides of the device to facilitate the
device moving. The speed of movements was about 10 cm per second
during the experiment.
[0050] FIG. 11(a) depicts the results of thickness measurement of
the press felt in paper production plant. The fabric is about 10%
thicker on one side than another, which typically happens when
pressure on press rollers is not uniform. An adjustment of the
roller pressure can be recommended as a result of the measurement.
The adjustment can prevent the fabric damage and also improves the
quality of produced paper.
[0051] FIG. 11 (b) shows results of the thickness measurement for
the same press felt after 23 days (upper line) and after 30 days
(lower line) of exploitation. Almost even wear of about 0.5 mm per
week is observed along all 8 meters of the fabric width.
[0052] The foregoing description of the preferred embodiment of the
invention has been presented for purposes of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise forms disclosed. Obviously, many
modifications and variations will be apparent to practitioners
skilled in the art. It is intended that the scope of the invention
be defined by the following claims and their equivalents.
* * * * *